Marine Corps faces tough fight to protect desert tortoise

Marine Corps Logistics Base Barstow is an installation focused on refurbishing gear, not training troops for war. Nonetheless, it's now the site of a pitched and bloody ongoing battle between species, officials say.

The environmental division at the California base is bringing the Marine Corps brand of ingenuity to bear in its fight to protect the desert tortoise, a federally listed endangered species native to the Mojave Desert, from the raven, a natural predator protected under the Migratory Bird Treaty Act.

While ravens historically haven't found much appeal in the region, that changed with the construction of Interstates 15 and 40, which were both built around the 1950s and intersect in Barstow.

"Here in the Mojave Desert, the U.S. Fish and Wildlife Service noticed that as the desert tortoises were declining — less and less juvenile tortoises were being observed during surveys — there is a direct correlation to an increase in raven population," Cody Leslie, the logistics base's natural resource specialist, said in a released statement. "When I say 'direct correlation,' I mean that, as the tortoises are decreasing in population, the ravens have increased by as much as 1,500 percent. That's a huge increase."

The desert tortoise, which is listed as vulnerable, can live to be 100. When it was added to the federal register of endangered species in 1990, there were an estimated 100,000 tortoises. But, according to a study published by the U.S. Fish and Wildlife service, an assessment of populations at six recovery units in 2014 estimated a population of under 86,000.

It's been years since Leslie has encountered a juvenile or hatchling tortoise, according to a base news release.

While ravens are known to go after juvenile tortoises, whose shells stay soft for up to the first decade of the animal's life, conservationists were troubled to discover that the birds will even attack adult reptiles, flipping them and pecking at vulnerable shell access points. A recent experiment by the Superior-Cronese Critical Habitat Unit using dummy tortoises found 43 percent of the dummies were attacked by ravens, according to the release.

"It's pretty gruesome," Leslie said in a statement.

Since officials can't kill the protected ravens, they've had to get creative. And like the larger Marine Corps, they've found drones to be a force multiplier. The Barstow environmental division has undertaken an effort it calls "Egg Oiling," according to the release. They send drones out to coat eggs found in raven nests with a silica-based oil, which essentially smothers the young inside the shell, keeping out oxygen needed for development.

Hatching baby desert tortoise.

(Photo by K. Kristina Drake)

"The ravens continue to sit on the eggs for the entire breeding season and do not continue to rebreed," the release states.

In addition to the drone-aided egg oiling, conservationists are asking base employees and other residents to make sure their trash is disposed of in closed containers and that no food, including pet food, is left accessible to the birds.

Leslie also asked locals to report raven nests and bird activity to the Environmental Division and not to leave any water sources out in the open.

The desert tortoise, which also faces non-raven threats such as viral herpes and Upper Respiratory Tract Disease, has long presented a training challenge for Marines, who also occupy tortoise territory at Marine Corps Air-Ground Combat Center Twentynine Palms in the Mojave. Marine officials have relocated gear and altered training plans in order to avoid disturbing the creatures.

This article originally appeared on Military.com. Follow @militarydotcom on Twitter.